In the new scenario of electrical energy competition and ancillary services market, it has grown the need and interest in developing and applying suitable real-time control systems for the grid voltages and reactive powers regulation. The portion of power flow that result in a net transfer of energy in one direction is known as real power (or useful or active power). That portion of power flow that is due to stored energy in the load returning to the source in each cycle is known as reactive power. Apparent power is the vector sum of real and reactive power.
The power factor is defined as the ratio of real power to apparent power. This definition is often mathematically represented as kW/kVA, where the numerator is the active (real) power and the denominator is the active and reactive power or apparent power. Power factor equals one when the voltage and current are in phase, and is zero when the current leads or lags the voltage by 90 degrees. If the load is purely reactive, then the voltage and current are 90 degree out of phase and there is no net energy flow.
For two AC power systems transmitting the same amount of real power, the system with the lower power factor will have higher circulating currents due to energy that returns to the source from energy storage in the load. These higher currents in a power system will produce higher losses and reduce overall transmission efficiency. A lower power factor circuit will have a higher apparent power and higher losses for the same amount of real power transfer. Thus, it is desirable to maintain a high power factor in an AC power system.
Reactive power, however, is necessary to maintain adequate voltage levels on a power grid. Without such voltage support, the transfer and distribution of real power would be adversely affected. For this reason, a transmission operator often requires a power generator to provide a certain amount of reactive power in order to connect a power grid run by the transmission operator. Typically, the provision of such required reactive power reduces the amount of real power that a power generator could otherwise supply and reduce the power factor of the power generated by the power generator.
The present invention proposes a novel solution to overcome such drawback by installing Static Var Compensator (SVC) at the generation side of the power plant to improve the power plant's active power throughput capability, extend dynamic reactive power regulation capacity, and enhance generator transient stability under system disturbances.
The concept of installing SVC at the generation side to share the required reactive power output of the power plant has been disclosed in U.S. Patent Application Publication No. US2011/181044 A1.
The present invention is directed to the method and apparatus for power plant dynamic reactive power regulation and transient stability improvement.